72 The American Geologist. February, 1902. 
which in one place have cut sixteen feet down into the shale 
below. 
At least 41 feet of stratified clay and sand were then depos- 
ited, containing leaves and trunks of trees as well as unios 
suggesting a warmer climate than that of Toronto at present, 
a climate like that of the middle United States. 
Conformably on this a series of peaty clays containing trees 
and other plants of a cool temperate climate was laid down to 
the thickness of 94 feet. 
Upon the clay rest 55 or more feet of stratified sand with 
trees of about the same kind. 
The greatest thickness of the series observed at one place 
is 186 feet, at Scarboro Hights; and the stratified sand and 
clay have the character of deposits formed in a large body of 
water as a delta. They could not have been so evenly and 
finely stratified if formed by river action on a land surface. 
The lake; which stood at least 152 feet above the present 
level of Ontario at the close of the delta formation, was then 
drained off to a level much below that of Ontario, and rivers 
began to cut valleys in the delta deposits. These valleys are 
not V-shaped gorges, but wide and with gentle slopes, the 
smallest of them, at the Dutch church, Scarboro Hights, be- 
ing more than 150 feet deep, 1,200 feet wide at the level of 
lake Ontario and about a mile wide on top. It is much more 
mature in appearance than the valleys cut by the present Don 
and Humber since the time of the Iroquois beach, for the latter 
have often steep cliff-like walls, even in loose materials, such 
as clay and sand. 
Then followed a great accumulation of glacial materials, 
four sheets of boulder clay with intervening stratified clay and 
sand, the whole 203 feet in thickness, resting on the eroded 
surface of the interglacial beds and largely filling the valleys 
just referred to. During this time the water of the lake rose 
to 360 feet above Ontario as shown by stratified clay, sand and 
gravel. 
Let us now try to sum up the minimum time necessary for 
the process which took place between the two advances of the 
ace. 
The first stream erosion, through the till and sixteen feet 
into the shale, may have demanded more than 100 years. In 
